Samuel (Ollie Gyani) was born prematurely and with a bust heart, and, according to the Daily Mail, it is a “miracle” that he is still alive. He is now seventeen and the big brother of another enormously feeble premature baby, whom he has taken the liberty of naming Jacob. It is unclear what would happen if Jacob lived and his parents, objecting to his premature name, decided to call him something else out of spite. But with Jacob for now, Samuel invites his two friends, the siblings Will (Joe Alwyn) and Tamsin (Polly Edsell), to his house in the dead of night. For he has an audacious plan which could save his baby brother’s life.

Yes, he has captured the tooth fairy (Claudia Jolly), and he plans to bargain with her for Jacob’s life. It may sound as if we are in for a whale of a time, but this outfit from Bristol will perform “Thirty Two Teeth” (which is presently playing at C Soco) as solemnly as if it was Ibsen. The siblings are thoroughly beastly, the brother snarls and the sister henpecks. Samuel stands about a little helplessly, a young Prospero without the wisdom, whilst the creature whom he has hauled out of fairy land is more Caliban than Ariel, as filthy and as restless as an ape, and dressed in bits of newspaper.

It quickly becomes very frightening. At one point, the fairy is left alone with the audience, and when she finally notices us for the first time, I am glad that I am sitting at the back of the theatre. The deep chord of terror which the writer, Penny Gunter, manages to reach, is the fear of losing your teeth, of waiting to be received in the dentist’s chair. The plot is largely senseless, with Samuel providing ever more unintelligible rationales for his actions, but the result is that we end up following the stark, demented logic of a nightmare.

The fairy lunges at the humans in calculated little attacks, frantic to tear their teeth out. Samuel nominates Tamsin to lose all of her teeth and he prepares to pull them out one by one with a pair of pliers. If he had resolved to kill her, I would not be nearly so troubled, but as I have not visited a dentist since I was eighteen, and my teeth consequently look as if they were painted by Picasso, the prospect of repaying that cumulating debt to the tooth fairy, and without the mercy of anaesthetic gas, leaves me blank with panic.

This play is not perfect. The casual dialogue is initially a bit too wordy, and the cast struggle to spit out their lines. The slide into nightmare is broken before the end of the play, and it is as if the dentist’s grip around our throat has relaxed. Indeed, for once we have found a play which is spoiled by too much subtlety, and after so much hard work, Gunter has surely earned the right to treat everybody to a bloodbath. But “Thirty Two Teeth” nevertheless manages to ride that most difficult of horses, theatrical horror, with great panache.

[I could only acquire the cast’s names from this review of an earlier performance in Bristol. Please inform me if I have got them all wrong. Ed.]